This project is guided by a psychobiological model of disease based on (a) the Center's "common pathways" model, (b) the existing literature concerning adaptation to cancer and other chronic illnesses, and (c) the literature on stress and coping. The proposed research tests the model by using it to construct two psychosocial interventions for women with breast cancer, and evaluating whether the interventions influence disease outcomes by altering the underlying psychological and behavioral pathways that the model identifies. Downstream effects on biological pathways and disease outcomes are also examined. The specific aims of the project are to: (1) implement and evaluate a two-arm intervention designed to enhance adjustment, and lower recurrence and mortality among women with early- vs. late-stage breast cancer; (2) determine the psychological, behavioral, and biological mechanisms through which the interventions operate; (3) assess whether the two arms of the intervention are differentially effective for women with different characteristics, most importantly early- vs. late-stage disease; (4) use the baseline data collected prior to the intervention to determine the nature and extent of difficulties faced by early- vs. late-stage breast cancer patients; and (5) determine how participants in the intervention differ from those who choose to participate. Four hundred and twenty women, age 25 and above, will be randomly assigned to one of two active arms of an intervention program or a treatment-as-usual control group. One active arm of the intervention will consist of group education sessions (lasting 1 hour/week for 8 weeks), in which women are provided with information about breast cancer and taught adaptive coping strategies and stress management techniques. The second arm of the intervention will consist of group peer support sessions (also lasting 1 hour/week for 8 weeks), in which the women will be encouraged to share their experiences in an attempt to provide a sense of emotional support, promote altruism among group members, and supply group members with an enhanced sense of purpose and meaning in life. Hypothesized predictors, mediators, and relevant outcome measures will be assessed prior to the intervention. Mediators and outcomes will then be reassessed, both when the intervention ends and 6-months later. Analyses will focus on evaluating the benefits of the intervention, and identifying who benefits from which intervention and why the benefit occurs.